In general, there are two methods for acquiring a printing image and displaying the image on a screen before a printing operation. The first method is to interpret a print command transmitted to a printer by a computer connected to the printer, and develop the printing data in units of C, M, Y, and K planes to be synthesized as a printing image. The second method is to transmit a print command from a host computer to a printer, and receive a printing image generated inside the printer-by the host computer which then displays the image.
In addition, in a network environment, there are two more methods for displaying a printing image on a screen. The third method is to interpret a print command transmitted to a printer by a printer server which locally connects printers to provide the network with printer functions, and develop the printing data in units of C, M, Y and K planes to be synthesized as a printing image in the printer server. The fourth method is to supply a printer or a printer server with a print command by a host computer, which requests the printer server or printer to perform printing through a network, then acquire from the printer a printing image generated inside the printer or printer server by the host computer through the network, and display the image.
Furthermore, in a printing system employing a computer which incorporates Microsoft Windows® as an operating system, printing data generated by an application program or the like is stored in a system-standard spool file. Therefore, the printing data stored in the spool file cannot be accessed freely. For this reason, a printer driver comprises a preview function which enables an access to printing data by spooling the printing data in its unique form (unique spooling) and performs printing-image generation for displaying a printing image (fifth method).
However, the above-described conventional art has the following problems to be solved.
In the first and third methods where a host computer interprets a print command transmitted to a printer and generates a printing image, although extremely accurate printing image data can be obtained, the size of image data increases in proportion to a printer resolution. Therefore, a large amount of storage area is necessary. This problem remains even in a case where a printer server generates a printing image in a network environment.
Furthermore, in the second and fourth methods where a host computer acquires a printing image generated by a printer based on a print command, although extremely accurate printing image data can be obtained, the size of the image data increases in proportion to a printer resolution. Therefore, not only a large amount of storage area is necessary, but also an increased amount of time is required for transferring the printing image from the printer to the host computer. In the network environment, this not only increases the data transfer time, but also increases a network traffic, and may cause a communication delay or disturbance.
Furthermore, in regard to the fifth method of using the unique spooling function of a printer driver in a printing system employing a computer which incorporates Microsoft Windows® as an operating system (OS), since the fifth method has a low affinity to the OS, it is necessary to continuously develop the unique spooling function in accordance with a future improvement or specification changes of the OS. Therefore, it raises a problem of an increased development cost.